The baby boomer generation is reaching old age and with old age comes cognitive decline and a concern for preventing and treating neurodegenerative diseases. It is suggested that physical activity and mental exercise can effectively treat and prevent cognitive decline. This paper will review three studies related to physical activity and cognitive decay.
Exercise is a preventative for cognitive decline. There is a large growth in the population of adults over the age of 65 in today’s society in America, yielding an increase of a population that is currently dealing with or at risk for neurodegenerative diseases (e.g., Alzheimer’s and Parkinson’s disease). Along with the growth of this population comes the growth of medical expenses reaching approximately $172 billion in 2010 (Alzheimer’s Association, 2010). The rise in the older adult population and the elevation in medical costs for neurodegenerative diseases demonstrate the need for an effective prevention and prescription for cognitive decay.
Exercise may be an effective prevention and treatment for cognition preservation and may even reverse some of the age-related declines in cognition. Contrary to pill form medication, physical activity is not accompanied by adverse effects to the body and is consistently related to an increase in brain mass and better cognitive performance. There has been extensive research on the effects of exercise on mental health. It is suggested that aerobic exercise has a neurogenesis effect on the brain forming new brain cells and blood vessels and boosts communication between neurons (Erickson, & Weinstein, 2011). New cells and blood vessels increases blood flow and the transportation of nutrients in the brain, delivering improved brain function and an increase in brain volume. In one study, elder adults were randomly chosen to participate in either a moderate-intensity aerobic walking group or a stretching and toning control group over a 6 month period (Colcombe et al., 2006). The aerobic group showed an increase in both gray and white brain matter, while the control group demonstrated a slight decrease associated to age-related brain atrophy. Research suggests that a combination of consistent aerobic exercise, motor skill exercises, and problem solving exercises demonstrate improvement in brain function and help maintain brain health (Colcombe, (2006); Erickson, (2011); Shaie, (1986)). This literature review will explore the effectiveness of aerobic, motor skill, and problem solving exercises as therapeutic treatment and prevention for neurodegenerative diseases.
Physical and motor fitness are both related to cognition in old age. A study was conducted to see if different dimensions of fitness (physical and motor fitness) were differentially associated with cognitive performance. Participants for this study were recruited from a member register of a German health insurance company called DAK (Voelcker-Rehage et al., 2010). The study included 72 male and female participants between ages of 62-79 years old who had normal vision and hearing capabilities. Delimitations to this study included persons who had any history of cardiovascular disease, neurological disorders, motor or cognitive restriction or metal implants. Participants completed four psychometric tests showing two primary abilities of higher cognitive functioning (executive control, perceptual speed) and a set of fitness tests involving two fitness dimensions (physical and motor fitness) (Voelcker-Rehage et al., 2010).
For cognitive assessment, four experimental cognitive tests from the Berlin Cognitive Battery (Li et al., 2004) were given reflecting executive control and perceptual speed. Perceptual speed was measured by the Identical Picture Test (Ekstrom et al., 1976) and a Visual Search Task (Hommel et al., 2004). For executive control, response time was measured by a modified version of the Flanker Task with three response conditions (Li et al., 2004). Working memory was measured by a letter n-Back Task with three difficulties (0-, 1-, 2-back) (Dobbs & Rule, 1989; Voelcker-Rehage et al., 2006). The Flanker Task was done in an MRI scanner so they could examine the effects that physical activity had on the brain. For motor assessment, fitness was tested by using a set of 10 tests representing two fitness aspects, (i.e., physical and motor fitness, (Voelcker-Rehage et al., 2010). The 10 tests assessed flexibility, hand tapping, feet tapping, agility, backwards beam walk, one-leg-stand with eyes open and closed, and fine coordination (Voelcker-Rehage et al., 2010). Physical fitness was tested my measuring grip force which indicated muscular strength and spiroergometry to indicate cardiovascular fitness. Each participant took the motor and cognitive tests in two individual laboratory sessions of about 2 hours each and sessions took place within 1 week (Voelcker-Rehage et al., 2010). On day 3, participants performed the Flanker Task in the MRI scanner (Voelcker-Rehage et al., 2010). It is assumed that the therapists who assessed the participants were well trained and qualified to do the tests. It is also assumed that participants were assessed in the same laboratory using the same therapists to assess each test.
Results and Discussion
Physical fitness was mainly related to executive control processes, while motor fitness showed a significant association with both the executive control and the perceptual speed tasks (Voelcker-Rehage et al., 2010). These findings suggest that fitness is differentially associated with perceptual speed and executive control. This study used a large number of tests and measured a large number of variables making the study hard to follow and it had a lot of variability. Future research should use one general assessment to measure fitness rather than a series of 10 different tests. The age range in this study was limited to older adults and it is unknown if these results are significant in other age ranges. Also, it is unclear how intelligent the participants were before being tested. If their IQs were not in a normal range, it could have affected results. Future research could benefit from assessing different age groups and testing participants’ IQ before conducting experimentation.
Can decline in adult intellectual functioning be reversed? A 14-year longitudinal study was conducted to investigate whether or not cognitive decline in the elderly could be reversed (Schaie & Willis, 1986). The sample included 229 older adults (male=97; female=132) between the ages of 64 and 95 from the Seattle Metropolitan area. All participants were or had been members of a health maintenance organization (Group Health Cooperative of Puget Sound) and most of them were Caucasian (Schaie & Willis, 1986). Delimitations to this study include subjects with any known physical or mental disabilities that would interfere with participation in the study, other ethnicities than Caucasian, and ages outside the range of 64 to 95.
Subjects were tested with the Thurstone (1948) Primary Mental Ability (PMA) Reasoning and Spatial Orientation measures and were classified as remaining stable or having declined over the prior 14-year interval (1970–1984) (Schaie & Willis, 1986). Subjects were assigned to either Reasoning or Space training programs based on their performance. If subjects declined on Reasoning, but not on Space, or vice versa, they were assigned to the training program for the ability showing decline. Participants who had remained stable on both abilities or had shown decline on both abilities were randomly assigned to one of the training programs. Space training subjects included 51 stables (male = 23; female = 28) and 67 decliners (male = 29; female = 38). Reasoning training subjects included 56 stables (male = 25; female = 31) and 55 decliners (male = 20; female = 35) (Schaie & Willis, 1986). The study had a pretest-treatment-posttest control group design. The Reasoning training group worked as a treatment control for the Space training group and vice versa (Schaie & Willis, 1986). A staff member visited the subjects’ homes and discussed specifics of the study, answered questions, assessed sensory handicaps that might obstruct participation, and confirmed whether the home was apt for conducting the training sessions (Schaie & Willis, 1986). Participants had two pretest sessions that lasted 2½ hours per session. Based on their prior longitudinal performance plus their pretest scores, subjects were assigned to either the Reasoning or Space training program (Schaie & Willis, 1986). Training consisted of five 1-hour individually conducted training sessions by two middle-aged trainers with previous educational experience working with adults and the majority of the subjects were tested in their homes (Schaie & Willis, 1986). The study does not specify where the subjects were assessed, or if testing occurred outside of the home. After training, subjects were evaluated on a posttest involving the same measures used at pretest and subjects were paid $100 for participating in the study (Schaie & Willis, 1986). It is assumed that the staff member that was sent to the participants’ home was qualified to assess the home and evaluate the subjects.
For the Reasoning training program, the pattern description rules used in problem solution were recognized. Four major types of pattern description rules (identity, next, skips, and backward next) were identified, comparable to those mentioned in previous literature ( Holzman, Pellegrino, & Glaser, 1982 ; Kotovsky & Simon, 1973). Practice problems and exercises were designed, based on these pattern description rules and participants were taught through demonstration, feedback, and practice techniques (Schaie & Willis, 1986). The following strategies for identifying the patterns were stressed in training: visual scanning of the series, saying the series out loud in order to hear the letter pattern, and underlining repeated letters occurring throughout the series. After forming a hypothesis for the pattern type, subjects were taught to mark repetitions of the pattern within the sequence and find the next letter needed to complete the pattern rule (Schaie & Willis, 1986). For the Space training, the PMA Spatial Orientation test was done to find the missing angle of rotation. Practice problems were created to show the angle rotations identified in the task examination (45°, 90°, 135°, 180°). Training focused on: creating terms for different angles; practice with manual rotation of figures prior to mental rotation; practice with rotation of drawings of familiar objects before introducing abstract figures; participant-generated names for abstract figures; and having the participant focus on two or more features of the figure during rotation (Schaie & Willis, 1986). These cognitive strategies were found in research on mental rotation ability preceding this study ( Cooper & Shepard, 1973; Egan, 1981; Kail, Pellegrino, & Carter, 1980). It is assumed that the trainers were effective in explaining all concepts of both the Reasoning and Spatial tests and that subjects understood them. The control group of this study received a training program different than those mentioned above, but the study does not specify how it was different.
Results and Discussion
The outcomes of this study showed that participants trained in each program on average showed significantly greater gains than did the controls receiving the alternate training program. Findings in this study included that training techniques can reverse cognitive decline over a 14-year period in a significant number of older adults. Results demonstrated that brain training improves the performance of older individuals that remain stable, and that the extent of training effects are not related to age, education, or income (Schaie & Willis, 1986). This suggests that staying mentally active could potentially reverse cognitive decline and aids in prevention of cognitive decay. The amount of training time in this study was relatively short and future research could benefit in seeing what happens with longer training duration. Specifying alternate training techniques and where subjects are assessed out of the home could also be beneficial to future research.
A study was conducted to examine the effects of aerobic exercise training, age, and physical fitness on memory-search performance. Participants included 28 men ranging from ages 30 to 58 years old. Subjects were recruited from an ad in a local newspaper and told that they were participating in a project designed to test the psychological effects of exercise (Blumenthal & Madden, 1987). Delimitations included people with cardiovascular disease or people with physical disabilities preventing them from effectively completing the tests. One group of 13 men engaged in supervised aerobic exercise 3 times a week for 12 weeks, while a second group of 15 men engaged in anaerobic exercise (strength training) for the same time period (Blumenthal & Madden, 1987). Participants’ reaction time (RT) performance in a memory-search task was tested both before and after the 12 weeks of exercise training. Subjects were randomly placed in either the aerobic or anaerobic exercise group.
Physiological and psychological tests were given both during a 1-week period preceding the beginning of their exercise program and in the first week following 12 weeks of exercise
training (Blumenthal & Madden, 1987). For physiological testing, a graded treadmill assessment was assigned to subjects using a modification of the Balke Protocol (Balke & Ware, 1959). Participants were required to run on the treadmill with incremental increase in incline grade of 1 MET per minute until complete exhaustion was achieved and they could no longer execute the exercise (Blumenthal & Madden, 1987). Heart rate measurements were taken with a Hewlett-Packard 4685-A Digital Cardiotachometer and oxygen consumption (VO2max) and carbon dioxide production were measured for each subject prior to exercise and during the second minute of each exercise stage (Blumenthal & Madden, 1987). The difference in VO2max between the first and second testing sessions indicated the magnitude of the aerobic training effect provided by the exercise program. Participants were tested individually in a laboratory. For memory testing, first, they were instructed about the procedure and had a few minutes to relax and get familiar with the lab. Subjects were then seated at a computer. The RT task was a version of the Steinberg (1969) memory-search model. On each trial, a memory set of either two, four, or six digits was shown on the monitor screen. There was no time restriction as to how long the subject could view the memory set. The subject pressed the space bar on the computer to begin the trial, which erased the current memory set and brought a warning signal to the center of the screen for 1 second. The interruption of the warning signal was immediately followed at the same location by an image. Subjects chose a yes or no response representing if the image was in the memory set or not. Answer submission erased the image and added a new memory set to the screen. Participant RT on each trial was measured from the initiation of the image. Each participant had one block of practice trials and five blocks of test trials at each session and each block was a randomized sequence of 18 yes-response trials and 18 no-response trials. For exercise testing, participants in the aerobic group exercised three times a week, under medical supervision, for 12 consecutive weeks and exercise sessions consisted of 10 minutes of stretching followed by 30-45 min of continuous walking or jogging (Blumenthal & Madden, 1987). For the first week all of the subjects were instructed to walk only but by the end of 3 months almost all of the subjects were jogging continuously for 35 min. Exercise intensity was prescribed to yield elevations of heart rate equal to 70%-85% of the maximal heart rate achieved on each subject’s initial treadmill test. Participants were taught to measure their own heart rates by carotid or radial palpation and they were to maintain their heart rates at (or above) their prescribed range more than 95% of the time and an exercise physiologist checked their heart rates 3 times per session. Participants in the anaerobic exercise group engaged in a strength and flexibility program. These exercise sessions included 10 min of stretching exercises followed by 30-45 min of weightlifting under physical therapist supervision. Weightlifting equipment was made available and subjects were instructed in the proper technique for using this equipment 2-3 times weekly for 12 weeks. Subjects were told not to engage in any aerobic exercise. All of the subjects were told to continue their usual eating habits, but there was no monitoring of their diets (Blumenthal & Madden, 1987).
Results and Discussion
This experiment found that physical fitness and age affected different components of RT performance. Subjects’ initial (Time 1) level of fitness accounted for 15% of the variance in the Time 1 intercepts and 19% of the variance in the Time 2 intercepts, with higher fitness being associated with faster RT in each case (Blumenthal & Madden, 1987). This study suggests that there is a significant difference in memory between more fit and less fit individuals. Future research should include initial aerobic performance and RT times to better demonstrate the relationship of if aerobic activity was the factor in better memory or if it was due to how fit the subjects were. Also, if one subject studied the memory screen longer than another subject, it could have caused them to do better on the test. The amount of time the subjects’ spent on memorizing the memory screen should be measured to provide more accurate data.
Aging is associated with cognitive decay and brain atrophy. Physical activity and mental exercise has been proven to significantly promote brain health and aid in cognitive decline prevention. The studies shown in this literature review further support this statement. Also, it is never too late to start exercising. Many of the results of these studies showed improvement in brain function after beginning exercises even in old age. There isn’t much research on whether or not exercise can also reverse or help other brain disorders like traumatic brain injury (TBI). Further research on the effects that exercise has on TBI or other brain related issues is encouraged.
Alzheimer’s Association, (2010). 2010 Alzheimer’s disease facts and figures. Alzheimer’s and Dementia 6(2):158-194.
Balke, B., & Ware, R. W. (1959). An experimental study of physical fitness of Air Force personnel. U.S. Armed Forces Medical Journal,10, 675-688.
Blumenthal, J. & Madden, D. ( 1987). Effects of aerobic exercise training, age, and physical fitness on memory- search performance. Psychology and Aging, 3(3): 280-285.
Colcombe, S.J., et al. (2006). Aerobic exercise training increases brain volume in aging humans. The Journals of Gerontology, Series A, Biological Sciences and Medical Sciences 61(11): 1166-1170
Cooper, L. B., & Shepard, R. N. ( 1973). Chronometric studies of rotation of mental images. In W. G.Chase ( Ed.) , Visual information processing,75-96. New York: Academic Press.
Dobbs, A.R. & Rule, B.G. (1989) Adult age differences in working memory. Psychology of Aging, 4, 500-503.
Ekstrom, R.B., French, J.W., Harman, H. & Derman, D. (1976). Kit of factor- referenced cognitive tests. Educational Testing Service (rev. ed.), Princeton, NJ.
Erickson, K., & Weinstein, A., (2011). Healthy body equals healthy mind. Journal of the American Society on Aging, 35(2): 92-98.
Holzman, T. G., Pellegrino, J. W., & Glaser, R. ( 1982). Cognitive dimensions of numerical rule induction. Journal of Educational Psychology, 74, 360– 373.
Hommel, B., Li, K.Z.H. & Li, S.C. ( 2004) Visual search across the life span. Developmental Psychology, 40, 545-558.
Kotovsky, K., & Simon, H. A. ( 1973). Empirical tests of a theory of human acquisition of concepts for sequential patterns. Cognitive Psychology, 4, 399– 424.
Li, S.C., Lindenberger, U., Hommel, B., Aschersleben, G., Prinz, W. & Baltes, P.B. (2004). Transformations in the couplings among intellectual abilities and constituent cognitive processes across the lifespan. Psychological Science., 15, 155-163.
Schaie, W.K. & Willis, S. (1986) Can decline in adult intellectual functioning be reversed? Developmental Psychology 22(2), 222-232.
Voelcker-Rehage, C., et al. (2010). Physical and motor fitness are both related to cognition in old age. European Journal of Neuroscience, 31(1), 167-176.